Imaging Findings in Patients With H1N1 Influenza A Infection

Background: Swine influenza (H1N1) is a very contagious respiratory infection and World Health Organization (WHO) has raised the alert level to phase 6 (pandemic). The study of clinical and laboratory manifestations as well as radiologic imaging findings helps in its early diagnosis.
Objectives: The aim of this study was to evaluate the imaging findings of patients with documented H1N1 infection referred to our center.
Patients and Methods: Thirty-one patients (16 men) with documented H1N1 infection were included in our study. The initial radiography obtained from the patients was reviewed regarding pattern (consolidation, ground glass, nodules and reticulation), distribution (focal, multifocal, and diffuse) and the lung zones involved. Computed tomography (CT) scans were also reviewed for the same abnormalities. The patient files were studied for their possible underlying diseases.
Results: The mean age was 37.97 ± 13.9 years. Seventeen (54.8%) patients had co-existing condition (eight respiratory, five cardiovascular, two immunodeficiency, two cancer, four others). Twelve (38.7%) patients required intensive care unit (ICU) admission. Five (16.1%) patients died. (25.8%) had normal initial radiographs. The most common abnormality was consolidation (12/31; 38.7%) in the peripheral region (11/31; 35.5%) followed by peribronchovascular areas (10/31; 32.3%) which was most commonly observed in the lower zone. The patients admitted to the ICU were more likely to have two or more lung zones involved (P = 0.005).
Conclusions: In patients with the novel swine flu infection, the most common radiographic abnormality observed was consolidation in the lower lung zones. Patients admitted to ICU were more likely to have two or more lung zones involved.

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